Interesting / strange code picked up from pluralsight training (functional programming)

raddevus

I was watching a very good intro to Functional programming on PluralSight (Functional Programming with C# | Pluralsight[^]) and the author / presenter created the following method (mine has altered var names).

public static class Helper{
public static T Tee(
T @inVal,
Action act){
act(@inVal);
return @inVal;
}
}

Now you can call that method like the following:

Helper.Tee("test", Console.WriteLine);
Helper.Tee(3.238, Console.WriteLine);
Helper.Tee (new {garbage="super"},Console.WriteLine);

Here's the output:

test
3.238
{ garbage = super }

It's loosely based on the following idea (why it's named Tee): tee (command) - Wikipedia[^] Just thought it was an interesting example and it made me think differently about things. After all these years of OOP I'm beginning to see the real value in the Functional paradigm*. *Obviously the included sample is not a huge example of Functional programming in and of itself.

Sander Rossel

How is that any different from calling Console.WriteLine("test"); etc.? It's just more code to call Console.WriteLine and you aren't chaining anything or using the Tee output :confused: Even worse, an Action<T> assumes a side-effect because it doesn't return a value. Or is Tee used to "hide" this side-effect? If I read the wiki page I'd suspect Tee does the Console.WriteLine and you can pass in a File.WriteText or something similar, but even then I fail to see how Tee is helping you. You could just as well call both methods.

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Bernhard Hiller

What a weird, but interesting, idea. I think a better example than Helper.Tee("test", Console.WriteLine); could be string result = Helper.Tee("test", Console.WriteLine).ToUpper(); That shows the "T" character of that function more clearly: since it returns the input parameter, you can chain a few functions.

Oh sanctissimi Wilhelmus, Theodorus, et Fredericus!

raddevus

I like your questions because I'm learning the concepts and determining how these things are important too. And I can tell by your questions that you have more functional experience than I do. Here's an example that may make more sense -- it's like a before and after test.

Helper.Tee(Helper.Tee(" _ before after _ ", Console.WriteLine)
.ToUpper().Trim()
.Substring(8,6),
Console.WriteLine);

That results in an output like the following:

_ before after _
AFTER

Because the Tee method returns the value methods can be chained just like the normal string methods and so you can see the BEFORE version of your string and then the AFTER version. I don't know if that is helpful either, but it's interesting. This was a very small portion of an example showing how to create fluent APIs.

Super Lloyd

this example is relatively convoluted and pointless. you find better and common use of functional programming in LINQ to Object! ;P

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raddevus

You are exactly correct about the return being the important part because it allows you to chain the methods. In another post I mentioned that you can do a "before and after" type of test which might look like:

Helper.Tee(Helper.Tee(" _ before after _ ", Console.WriteLine)
.ToUpper().Trim()
.Substring(8,6),
Console.WriteLine);

That results in an output like the following:

_ before after _
AFTER

raddevus

Yes, it does look that way...and I'm learning this stuff myself. However, I've provided a slightly better example in reply to Sander at: The Weird and The Wonderful[^] That at least makes a bit of sense. :)

Super Lloyd

it's cute, you are learning new stuff. that is good. :) The Tee code sample is contrived though, simply because it can be rewritten much more mean and lean like

var value = ...;
action(value)
// ... continue ...

it was, to put it bluntly, grossly over engineered, and should not be done in real work project! :-o However here is something like the given Tee function that could be more useful

public static class Helper
{
public static IEnumerable<T> Tee(this IEnumerable<T> enumerable, Action<T> action)
{
foreach (var e in enumerable)
{
action(e);
yield return e;
}
}
}

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Richard Deeming

It might help if you gave the method a name! :-D

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Richard Deeming

This definitely looks like a case for an extension method[^]. :)

" _ before after _ "
.Tee(Console.WriteLine)
.ToUpper().Trim()
.Substring(8, 6)
.Tee(Console.WriteLine);

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Super Lloyd

oops.. corrected! :-\

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raddevus

Ah, yes, that would be even better. Makes far more sense that way. :thumbsup:

raddevus

That was interesting to me so I altered the Tee method to make it an extension method. Simply add the _this_ to the first param T and your code works now.

public static class Helper{
public static T Tee(
this T @inVal,
Action act){
act(@inVal);
return @inVal;
}
}

" _ before after _ "
.Tee(Console.WriteLine)
.ToUpper().Trim()
.Substring(8,6)
.Tee(Console.WriteLine);

raddevus

Ohh...look...I've really gone crazy with this now.

public static class Helper{
public static T Tee(
this T @inVal,
Action act){
act(@inVal);
return @inVal;
}

public static Byte\[\] GetBytes( this String @inVal){
	Byte \[\] outBytes = new Byte\[@inVal.Length\];
	int loopCount = 0;
	foreach (Char c in @inVal){
		outBytes\[loopCount\] = Convert.ToByte(c);
		loopCount++;
	}
	return outBytes;
}

public static String DisplayBytes(this byte\[\] inBytes){
	String outVal = String.Empty;
	foreach (Byte b in inBytes){
		outVal += Convert.ToString($"{b} ");
	}
	return outVal;
}

}

Try it like this and you get before and after again:

"What up!"
.Tee(Console.WriteLine)
.GetBytes()
.DisplayBytes()
.Tee(Console.WriteLine);

Output looks like:

What up!
87 104 97 116 32 117 112 33

:cool: Well, it's fun.

Lost User

It doesn't copy stdin to stdout. The only thing in common with "tee" is in the amount of parameters.

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^] "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

raddevus

Yes, you are correct. I think the point that the author/presenter was attempting to make is that you can output the value and continue processing the value as input to yet another function. That's why the author/presenter named the method Tee (which I hadn't seen before). I looked it up and found the associated wiki article and just thought that was an interesting piece of history.

Lost User

raddevus wrote:

I think the point that the author/presenter was attempting to make is that you can output the value and continue processing the value as input to yet another function.

Like a decorator..

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^] "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

raddevus

Eddy Vluggen wrote:

Like a decorator..

cue Madonna

...touched for the very first time...

:laugh: I could not pass that up. Ignoring the bad joke (if possible) I think your point is really interesting, because it is like a decorator. Also, in an effort to completely beat this dead horse, how about the following addition? If, nothing else, the added method has a great name : see SpaceOut.

public static class Helper{
public static T Tee(
this T @inVal,
Action act){
act(@inVal);
return @inVal;
}

public static Byte\[\] GetBytes( this String @inVal){
	Byte \[\] outBytes = new Byte\[@inVal.Length\];
	int loopCount = 0;
	foreach (Char c in @inVal){
		outBytes\[loopCount\] = Convert.ToByte(c);
		loopCount++;
	}
	return outBytes;
}

public static String DisplayBytes(this byte\[\] inBytes){
	String outVal = String.Empty;
	foreach (Byte b in inBytes){
		outVal += Convert.ToString($"{b:D3} ");
	}
	return outVal;
}

public static String SpaceOut(this string @inVal){
	StringBuilder spacedItem = new StringBuilder();

	foreach (Char c in @inVal){
		spacedItem.Append($" {c}    ");
	}
	Console.WriteLine(spacedItem.ToString());
	return @inVal;
}

}

Now you can do this:

"What up!"
.Tee(Console.WriteLine)
.SpaceOut()
.GetBytes()
.DisplayBytes()
.Tee(Console.WriteLine);

And you will get the following:

What up!
W h a t u p !
087 104 097 116 032 117 112 033

Additionally interesting (or not) is that SpaceOut simply passes the input string along with no change since you only want the input to be printed with the extra spaces but don't want the output altered in this case. I got a million of 'em! :laugh:

Lost User

:laugh:

raddevus wrote:

I got a million of 'em! :laugh:

Is that due to .NET being functional, or due to OO and your result being an object? :-\

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^] "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

Nelek

You look like a kid with brand shiny new shoes :rolleyes: :rolleyes: ;P ;P :laugh: :laugh:

M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.